Radio air navigation indicator



Nov. 4, 194 7.

w. D. HERSHBERGER RADIO AIR NAVIGATION INDICATOR Filed Nov. 2, 1942 3 Sheets-Sheet l Nov. 4, 1947. w. D. HERSHBERGER RADIO AIR NAVIGATION INDICATOR Filed Nov. 2, 1942 3 Sheets-Sheet 2 r O t n e U n 3 ttorneg NOV- 4 1947 w. D. HERSHBERGER 2,430,292

RADIO AIR NAVIGATION INDICATOR Filed Nov.- 2, 1942 3 Sheets-Sheet I5 .LINE 1NR .NNY

(ttomeg Patented Nov. 4, 1947 more AmlNAviGArioN melee-Toit William-D@ Hershbe-rger, Princeton,- N; J assigner to Badia Corporation of America, incorporationoffllelaware Amplieation` N oyember 2, 134.2, Serial. Nel 16e-2.91.

(Cl. Z50-14:62)

EirClaims.` 1t

My invention relatesv to radio-echo or similar; systems fortranglo-measurements and particularlyto aV radio system/ forfmeasuringangles such as the.V angle 1 formedby-a linen fromm an? aircraft to an ,object on the` earthsffsurfaee and a perpendicular line from the-vaircraftt to earth.V Theiob;- ject maybe ashiponother target to be bombedY from the air-craft;

An .object of `theinvention-is tofprovide an irnprovedmethod-f of'` and: means` for measuring; an angle between Lines--V joining; a1 pointof-v sig-nal radiatiomand ytwo poi-nts oneavsurface whereone ofstha` other-angles oii the triangle for-med;Y by saidlines andalinehetweenI said two points on said surface-.ist a=xed'lmown-angle-.

A furtherobjectief-the invention is to provideV an improved system ofjthe above-described type: for determininghfthesaidgangie between thepfer,` pendiculac4 andjl the- 1ineto tina target.l or other reecting surface:

A furtherlobjeotofthe invention iste Eroi/ide en improved erstemV Whieh measurement. oi the said eneie is independent: Qfrtne. ettitueeof the aircraft,

A further obieet` oi'the-iriveatoniete provide. an improved sy'eteml of the above.:fleseifi.leed..typeV forv determininathe ealdang eyenthouehthe Shipor: other terget'ienot visible.V

A furtherobieet of `the.Ainvention.i.s .tonrovide an improvedV systengiA oi the, aboyef-deseribedftyne which. the. angle rrieasiir.ement may, lee;V reed. directly ironia .seele ortheiike- A i Still iurtlier. oleieet, of. thet invention4- ie to provide an. improved.. eyetem. for lenditia oi 1 aire-- eraftby. instrumenta 1n one preierredemhodiment-.of .theinverltiem en aircraft is.. provided. with i aradiofnuleefecho; system. which` radiates eSignal.. downward. and. f erwercl whereby reileetioosthet ere e measure of altitude. willlbereeeived from the earth-dit-` reetly below the.. planelwhileother refleetioiief. will bereeeivedrom. the target-ahead..- Sineeethet o Hiring. refl ,etitme4 Wilt hefameeelire et; thealtitude, or., distance. eernendie 1er to the. earth, the. angle.; e, between. this;` i! -Pendieulao line. enditheline yfrom theaircraftto. the.teieeeti` een.. be. determnedwhen..the/rangei# distante tothe targetis alsofknown. The latter distance isA shown by a leitet OGcurring reflection vfrom the target. Fromlthe La ctthat.` the distance tothe,

" ineorie embedimeetof the invention` target divided bythe altitude is .the secantofthe;

anale .0, the .angle 0. mayV eeealeulated- In eef eoldtnee with myA invention, however, the 1vappa?. ratueieso desienedthetntbe angle eisreedr .dh

This Amay-be accomplished in accordance with` my inyention by causing the cathode ray of the indicator tube tofbe deflectedA alternately along:

two deection paths o r tracesy one of them being a vertical tracefproducedA-by a sawtooth wave o n theverticall deflecting plates only and the other being atracepositioned atan angle'wth respect;

to they vertical traceV and; producedby applying the saw-tooth toboth the-vertical and the h ori` zontal deieeting4 plates; The altitude and target pulse indicationsf appearq` onh thesel traces. The desired angled (Fig,` 2-) mayv-bedetermined by keepngthe two-tracesr of equal length` andA by, making the ang-ie@ (Fig- 3)' between them siich that the targetpulseindication on the angulariy located treeeendthle altitude pulse indication .on the vertical Vtrace fall on the saine horizontal line, i@ e by. Ilflekitigv them horizontally coincidenti. The eneleobetvveeritheptwo traeesfis new equal. to the desired-*angie Q andwmiaybe read from an angle Seele merkcienthe ieee ofthe-indicator tube. be deseldf herel'lfl The ioveritioziwill` bereitet. understood from the following descriptionl .taken in connection with the eeeompanriiiadrewiriain which Figure 1 is.. a .blockx andA cir-.Cuit` diagramV4 showe Figure 2, is.. a diagram .showingV the; relation be; tween.Y theVY altitude echo... the` tereeteehe path and. the. anale. 0!

rieure .3 is@ .view represen.tinel thetsereenend ofthe indiaior tube o Fig; lA with cathode ray traces and pulse indicationsy thereon as: they appear when'utiiizing theiembodiment ofvEig.V 1,A

Figure 4. isV adiagranrillustratng the desired glide nath for aoeirplaneoi apertieulertypein makingalandng,

Figure. is aNiewiwhieh is: the same as thatoi` Fig. 3exeept.that it. illustrates. the tracesand pulse indications for the condition when-the `sys-` tem .of Fier 1 employed fer making.; en. instrument lending..

Figure 6 isa block. and circuitk diagrariiillusf,r trating another embodiment-@ofthe invention that isepertieulerlvf adapted for useintmaldne inetrufA nient; landings;

Figure Tisaa view-regresentingfthe screen end of.: the iridieetoe tubeof; Eig.; 6-W.ith.- the.M Cathode.V rey tratesA and ulse iridieatietlefthereon; and;

Figllre ie offerente-showing. t1 1vv1eft` right imitation ie eeeliedtothelsyetem eerie; se

Other embodlmenteeilthe invention. will.

2,430,292 .if .I

In the several gures, like parts are indicated by similar reference characters.

In Fig. 1, a high frequency radio transmitter lll, which is mounted on an aircraft l2 (Fig. 2), is keyed by means of a pulse keyer i3 connected to a keying pulse generator lli through a delay network l5 to radiate short radio pulses downward and forward from a suitable antenna sys-j tem l5, which is illustrated as a dipole in a parabolic reiiector. The transmitted pulses may occur at a rate of 3500 per second and have a duration of 0.3 microsecond, for example.

The reflected or echo pulses are picked up by a suitable antenna such as a dipole 2| and s upplied to a receiver 22 (also on the aircraft) which amplies and demodulates them. They are further ampliiied by an amplifier 23 and applied through a coupling capacitor to a pair of horizontal denr ilecting elements 2.1 and 21a of a cathode ray in.- dicator tube 29. The cathode ray tube 29 may be of conventional design and is provided with a pair of vertical deflecting elements 3l and Sia positioned at right angles to the other pair of elements.

A deflecting Voltage generator 35 supplies a linear sawtooth voltage across an output resistor 31. This deflecting voltage is applied in the manner described below through manually adjustable potentiometers 38-3811, 39 and .4l to the deecting elements of tube 29. The sawtooth generator 36 is synchronized with the pulse transmission by means of pulses from the pulse generator I4 supplied thereto through a conductor 42, an amplifier 43 and a conductor dfi.

The upper end of resistor 38 of the gain control potentiometer Sii-38a is connected through a relay armature 45 either to an intermediate point on resistor 31 or to the upper end of resistor 31, the first position being for the operation when measuring angles as illustrated in Fig` 3. It is only for blind landing operation or the like that a switch 41 is closed whereby the armature 53 is pulled periodically into contact with the up-per end of resistor 31 by a relay coil 4S.. Such periodic operation of the armature 46, with the resulting periodic change in magnitude of cathode ray delection is obtained by means of a cam operated switch 5l driven by a motor 52.

The lower end of resistor 38 is connected through a variable tap 53 to a point on the resistor 38a which is connected at each end through ground to the lower end of output resistor 31. Moving the tap 53 in either direction from the center position results in a reduction in the amplitude of the deflecting voltage applied to potentiometer resistors 39 and 4| since therelative circuit impedances are such that there is substantially no change in the current flow through the resistors 38 and 38a resulting from a change in the position of the tap 53. Opposite ends of resistors 39 and 4|, respectively, are connected through a resistor 54 to a point on resistor 38. The other ends of resistors 39 and fil are grounded.

Horizontal deilecting voltage is supplied periodically from resistor 4l to the delecting elements 21-21a through a variable tap 55 and a relay armature 51. Vertical deflecting voltage is supplied from resistor 39 to the vertical delecting elements 3I--3la through a variable tap 55 and a relay armature 59, this voltage being supplied alternately with reduced amplitude (depending on the position of tap 58) and with full amplitude. When it is supplied with Vfull amplitude, the armature 59 is in its lower position and the armature 51 is disconnected from the horizontal deflection supply whereby the vertical deilection trace 5l (Figs. 1 and 3) is produced.

During the instant that the vertical deflection voltage is supplied with less than full amplitude, the armatures 59 and 51 are in their upper positions and the cathode ray is being deflected both verticalhr and horizontally'by amounts determined by the positions of the taps 53, 56 and 53 which are ganged together for manual adjustment by operating a control knob 62 as indicated by the broken lines. This simultaneous vertical and horizontal deilection produces the trace 53 (Figs.

. ously by the closing of the cam operated switch 5 l When the taps 58 and 56 are positioned at` points where the vertical and horizontal voltages Y are equal, the trace 63V is at 45 degrees with re-I spect to the vertical trace 5l and is of minimum length for a given amplitude of deiiecting volt-y age. Therefore, when taps 58 and 56 are so po` sitioned, the tap 53 is positioned at the center of.' resistor 38a, this being its position for maximum. voltage. If the control knob 62 is turned to movethe taps 55 and 58 to the right of the above-men tioned equal-voltage position, the Vertical deflection is decreased in amplitude and the horizontal'. deflection is increased in amplitude whereby the: trace 63 swings away from the vertical trace 6l.. Simultaneously the tap 53 moves to the right to' decrease the amplitude of the deecting voltageI by the correct amount for keeping the length of the trace unchanged. Likewise, if the taps 55, 58 and 53 are moved to the left of said position the trace 63 swings toward the vertical trace 5|. AS before, its length does not change. In order to make the amplitude of the deflecting voltage decrease in the desired manner as the tap 53 is moved, it may be desirable to have the resistance of resistor 38a tapered instead of having it change linearly with respect Vto the position of the tap 53.

The cam switch 5| preferably is closed periodically at a rate that is high enough to make the traces 6l and 03 appear to an observer to be on the cathode ray screen at rthe same time.

In order to determine the angle 0 between the vertical and the line of sight to a target (Fig. 2), the potentiometer knob 62 is adjusted until the angular trace 63 is swung through such an angle qi that the target echo pulse indication T thereon and the altitudeecho pulse'indication A of the vertical trace 6l are horizontally coincident, as shown in Fig. 3. The condition of horizontal coincidence is obtained when the abovementioned indications 'I' and A fall on the same horizontal line such as one of a plurality of lines'61 marked on the face of the tube 29. The angle gb now equals the angle 0 and its value may be read at the point :r on an angle scale 68 where the end of trace 63 falls on or adjacent to the angle scale. The reason that the above-described procedure gives the desired angle is that the geometry of the two cathode ray traces 6| and 63 and the horizontal line of coincidence correspond exactly to the geometry of the altitude, target distance and ground level, respectively, indicated in Fig, 2.

My system may be employed for instrument landings of airplanes if the landing field is provided with a marker such as a reector or retransmitter to give the pulse-echo indication T. For example, an airplane equipped with my system can be brought into a landing iield along a straight line glide path if the pilot will keep entornos l Iindications A :and T, respectively, remain :horizontally lcoi'ncident.

A.Some pilots prefer changing .the .angle of the glide .path #during a landing as shown, by way of'zexamplain .Fig.i4. An airplane may be 'landed fin this Fway with my system and without adjustving v'the .-.control knob B2 sif the switch d] (Fig. l) `-is closed. This .pulls the .armature E6 against its might-hand contact .point whereby the deilecting voltagefis of increased `amplitude during the time the cathode ray is deflected vertically along the :trace FH (Fig. This gives .the vertical trace fan expanded scale `which `is A.desirable 'because of ithe slow .altitude of the `airplane during landing. The ,altitude Vindication .A .and the target or marker indication T appear on the .useful lengths of the `traces 1i and T2, respectively. The .target or `marker pulse `T `may not appear on the trace 5H (although it always appears von trace l2) or .it .:may appear :on trace only `when the landling :is substantially completed. The altitude inldication .Awill not appear on the useful portion `of trace 2; :instead :it will be near .the upper end :oif fthe trace A'|2, or may `not even be visible on .trace '1.2 (although it always appears on trace 1|). A ,plurality of lines `such as m, 11., o and r2 may Vhe .drawn :across the face of the tube 29 to intersecttheztraces "ill and 'i2 iat the points where Athe pulse `indications `A and T, respectively, will .fall if the .airplane is coming in at `the desired 1glide angle.

-For example, at 40001from the marker (Fig, 4) rthe pilot has dropped toan altitude of 500' where the proper glide angle is `indicated by the 72 line m. It `should be noted that "72 is the value of the angle d (Fig. 4) rather than the value of the glide angle itself. The airplane may be held at the indicated glide angle until point 2 (Fig. 4) is reached, at which point the angle may be changed to that indicated by the 5.7 line 11,. Similarly, the glide angle may be changed at other predetermined altitudes as the airplane approaches the runway. In practice, a pilot would tprobablychange thegl-ide angle gradually, Vwatching the altitude and marker indications to see that the altitude and marker indications A and T, respectively, are approaching the index lines m, n, o, etc., in the proper manner.

Fig. 6 illustrates another embodiment of the invention which is designed particularly for the instrument landing of aircraft. In this embodiment the sawtooth deflecting voltage is applied to the vertical deflecting plates 3|' and Sla only. The simultaneous application of centering voltages results in the production of vertical traces 16 and as shown in Fig. 7. Just as in Fig. 5, the trace 16 for indicating altitude has an expanded scale.

The traces 'H6 and 'Il are obtained by applying the sawtooth deecting voltage to the deflecting plates 3| and 3 la through one of the two contact points 13 and 'I9 and a relay armature 8|. The armature 8| is pulled from one contact point to the other by a relay coil 82 that is energized by a switch 83. The switch 83 is operated by a cam S4 which is driven by the motor` 52.

When the armature 8| is in the position shown for producing the expanded scale trace 16, a positive centering voltage is applied to the deflecting plate 21 through a relay armature 86 and a resistor 8l. This pulls the vertical deiiection to one side of center. When the armature 8| is in the other position for applying a deflecting voltage of smaller amplitude, thus producing the 6 4trace ll, the armature 86 is in its other Aposition to .apply a negative bias to the deilecting plate 21. Thispulls the vertical deection to the other side vof center. The armature ASli is actuated 'in vsynchronism with the .armature 8| `by a relay coil 88.

The operation of the system is similar to that .described in connection with Fig. 5. A plurality `or lines such as d, e and f are drawn across the face-of the tube `29 Vto intersect the traces '|-8 and -11 at the points where the altitude and target (marker) pulses A and T, respectively, appear when the air-plane is on the-desired glide path.

Preferably, the system of Fig. 6 includes left- :rig-ht indication. This may be provided by supplying the output of transmitter IS through a left-right switching device 89 to a pair of directional antennas 9| and 92 having `overlapping radiation patterns. Switching device `3S is driven by the motor 52 which also drives the cam opervated switches -93 and 9d. Switches 93 and 94 contro-l `a -pair kof relay armatures 97 and S, `re speCtiVe'ly, to apply the echo pulses alternately -to the horizontal defiecting plates 21a and 27 respectively. Thus, Athe cathode ray is deflected `to the left by the echo pulse when the radiation lis from .the antenna having the left-hand radiation pattern and it is deflected to the right when .the radiation is from the other antenna. When `the airplane on which the ksystem is mounted is headed directly for the landing eld marker, 'the left and right deflections are of the same amplitude-and the pilot knows he is approaching the runway correctly. This condition is illustrated .atA and T in Fig. 7.

One satisfactory switching sequence is illustrated in Fig. 8 where'left and right switching periods 'are shown at Land R. The corresponding switching periods to produce the 'altitude and range or Ymarker traces 16 and Il are Vshown at alt and rangej respectively. It will .be seen that one :altitude trace T6 and 'one range trace are produced while signal is radiated toward the left. These two traces are again produced while signal is being radiated toward the right. It will be understood that the rate of switching is not critical but with a given cathode ray tube screen having a certain persistence of uorescence it should be high enough to make the altitude and range traces visible simultaneously without too much dicker.

I claim as my invention:

1. In a system for indicating the angle between the perpendicular and the line of sight from an aircraft to an object on the earths surface which comprises means for producing a first cathode ray trace, means for producing a second cathode ray trace which intersects said rst trace at an adjustable angle, means for adjusting said angle, means for radiating energy downward and forward from said aircraft whereby it is reflected from said surface and from said object, means for utilizing said reected energy to produce markings on said cathode ray traces which indicate the altitude of said aircraft and its distance from said object, and a plurality of index lines which intersect said first trace at the altitude indications and which intersect said second trace where the object indications appear for a given value of said angle to be indicated after an adjustment of said adjustable angle.

2. The method of determining the angle between the perpendicular and the line of sight from an aircraft to an object on the earths surface which comprises producing a vertical cathode ray trace, producing a second cathode ray trace positioned at a certain angle to said vertical trace, radiating energy downward and forward from said aircraft whereby it is reflected from said surface and from said object, utilizing said reected energy to produce markings on said cathode ray traces which indicate the altitude of said aircraft and its distance from said object, and adjusting the angular position of said second trace with respect to the vertical trace to a position where the object marking thereon is horizontally coincident with the altitude marking on the vertical trace while maintaining the same rate of movement of the cathode ray along the two traces whereby said angle between traces is equal to the angle between said perpendicular and said line of sight.

3. A method of indicating on the screen of a cathode ray tube the angle between a line from an aircraft to an object on the earths surface and a line perpendicular from the aircraft to the earth, said method comprising transmitting radio pulses toward the earth from said aircraft and producing alternately a vertical deflection only of tthe cathode ray and a simultaneous vertical and horizontal deflection of the cathode ray, said deflections being initiated at approximately the time of transmission of each pulse and starting from the same point on the screen, receiving said pulses after reection and utilizing the received pulses to alter the cathode ray during its deflections, and adjusting the relative amplitudes of the simultaneous vertical and horizontal deflections to values such that the altitude indication on the vertical sweep and the target indication on the angular sweep are horizontally coincident whereby the angle between said vertical sweep and said angular sweep is the desired angle.

4. In a system for determining the angle between the perpendicular and the line of sight from an aircraft to an object on the earths surface which comprises means for producing a vertical cathode ray trace, means for producing a second cathode ray trace positioned at an adjustable angle to said vertical trace, means for radiating energy downward and forward from `said aircraft whereby itis reflected from said surface and from said object, means for utilizing said reflected energy to produce markings on said cathode ray traces which indicate the altitude of said aircraft and its distance from said object, and means for adjusting the angular position of said second trace with respect to the vertical trace to a position where the object marking thereon is horizontally coincident with the altitude marking on the vertical trace whereby said angle between traces is equal to the angle between said perpendicular and said line of sight.

5. In a system for indicating on the screen of a cathode ray tube the angle between a line from ,an aircraft to an object on the earths surface and a line perpendicular from the aircraft to the earth, means for transmitting radio pulses toward the earth from said aircraft and for initiating alternately at approximately the time of transmission of each pulse a vertical deection only of the cathode ray to produce a vertical trace and a simultaneous vertical and horizontal deflection of the cathode ray to produce an angular sweep, means for receiving said pulses after reflection, means for applying the received pulses to said tube to alter the cathode ray during its deections, and means for adjusting the relative amplitudes of the simultaneous vertical and horizontal deiiections to values such that the altitude indication on the Vertical trace and the target indication on the angular trace are horizontally ycoincident while maintaining the same rate of movement of the cathode ray along both traces whereby the angle between said vertical trace and said angular trace is the desired angle.

WILLIAM D. HERSHBERGER.

REFERENCES CITED UNITED STATES PATENTS Name Date Hunter Dec. 17, 1940 Number 

